feat: s3proxy backend

This backend redirects incoming requests to another s3 service.
This will use the incoming credentials to setup the client
requests to the external s3 service. So the IAM accounts (or
root account) must match what the external s3 service expects.

backend/s3proxy/client.go

@@ -0,0 +1,86 @@
+// Copyright 2023 Versity Software
+// This file is licensed under the Apache License, Version 2.0
+// (the "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package s3proxy
+
+import (
+	"context"
+	"crypto/tls"
+	"fmt"
+	"net/http"
+
+	"github.com/aws/aws-sdk-go-v2/aws"
+	v4 "github.com/aws/aws-sdk-go-v2/aws/signer/v4"
+	"github.com/aws/aws-sdk-go-v2/config"
+	"github.com/aws/aws-sdk-go-v2/credentials"
+	"github.com/aws/aws-sdk-go-v2/service/s3"
+	"github.com/aws/smithy-go/middleware"
+	"github.com/versity/versitygw/auth"
+)
+
+func (s *S3be) getClientFromCtx(ctx context.Context) (*s3.Client, error) {
+	acct, ok := ctx.Value("account").(auth.Account)
+	if !ok {
+		return nil, fmt.Errorf("invalid account in context")
+	}
+
+	cfg, err := s.getConfig(ctx, acct.Access, acct.Secret)
+	if err != nil {
+		return nil, err
+	}
+
+	return s3.NewFromConfig(cfg), nil
+}
+
+func (s *S3be) getConfig(ctx context.Context, access, secret string) (aws.Config, error) {
+	creds := credentials.NewStaticCredentialsProvider(access, secret, "")
+
+	tr := &http.Transport{
+		TLSClientConfig: &tls.Config{InsecureSkipVerify: s.sslSkipVerify},
+	}
+	client := &http.Client{Transport: tr}
+
+	opts := []func(*config.LoadOptions) error{
+		config.WithRegion(s.awsRegion),
+		config.WithCredentialsProvider(creds),
+		config.WithHTTPClient(client),
+	}
+
+	if s.endpoint != "" {
+		opts = append(opts,
+			config.WithEndpointResolverWithOptions(s))
+	}
+
+	if s.disableChecksum {
+		opts = append(opts,
+			config.WithAPIOptions([]func(*middleware.Stack) error{v4.SwapComputePayloadSHA256ForUnsignedPayloadMiddleware}))
+	}
+
+	if s.debug {
+		opts = append(opts,
+			config.WithClientLogMode(aws.LogSigning|aws.LogRetries|aws.LogRequest|aws.LogResponse|aws.LogRequestEventMessage|aws.LogResponseEventMessage))
+	}
+
+	return config.LoadDefaultConfig(ctx, opts...)
+}
+
+// ResolveEndpoint is used for on prem or non-aws endpoints
+func (s *S3be) ResolveEndpoint(service, region string, options ...interface{}) (aws.Endpoint, error) {
+	return aws.Endpoint{
+		PartitionID:       "aws",
+		URL:               s.endpoint,
+		SigningRegion:     s.awsRegion,
+		HostnameImmutable: true,
+	}, nil
+}